A lot is going to depend on your budget. You mention Festool so I would assume your willing to pay for a good sander. In that range I would suggest looking at Mirka Deros or the SurfPrep DC brushless sanders. They both have dust collection (via a vac, dont know if self dust collection means you want it with a bag on board). But both of those options are going to set you back 500 bucks a pop.
The jittering you speak of with the dynabrade and 80 grit I fear is going to be a possibility with any aggressive sander, coarse paper, and operating at less than full speed. Every sander Ive owned, if you run coarse paper and your not at the full rated speed of the sander, it will rattle you all over the place.
We find that with quality, aggressive, sanders you can generally start sanding a couple grits higher than you normally would due to their performance and you can also stop sanding a grit or two lower than you normally would and still have good finish.
Was the 3M sander you tried electric? Ive wanted to get my hands on one of the 3M electric Dynabrades but my local distributor doesnt ever deal in them so Ive never been able to try one. They look like they may be rebranded.